The present invention generally relates to a temperature controller. In more detail, the invention relates to a temperature controller which is suitable for controlling the temperature in an incubator or an oven.
In the incubator which is used for the cultivation of microorganisms or cells or the oven which is used in various kinds of temperature tests for materials or parts, it is required that the temperature in a chmaber is kept at a desired level during the cultivation or test period. Hence, there are provided a heater and a temperature controller which controls the electric current as supplied through the heater and keeps the temperature in the chamber at the constant level.
FIG. 1 shows a conventional example of a temperature control system in the apparatus as mentioned above.
A first temperature controller 6 and a second temperature controller 8 respectively detect the temperature in the chamber and controls a first power controller 7 and a second power controller 9 which correspond to the first temperature controller 6 and the second temperature controller 8 respectively. The temperature of the first temperature controller 6 is the one which is aimed at, and the second temperature controller 8 has a temperature which is higher than the set temperature of the first temperature controller 6. The first temperature controller 6 turns on the first power controller 7 if the temperature in the chamber is lower than the set temperature, while the second temperaure controller 8 turns on the second power controller 9 if the temperature in the chamber is lower than the set temperature. Therefore, in case the temperature in the chamber is under the control of the first temperature controller 6, the second power controller 9 is always turned on, and the electric current which is supplied through the heater 5 is controlled by the first temperature controller 6. If there is caused a trouble in the first temperature controller 6, so that the temperature in the chamber starts to be raised, the control by the second temperature controller 8 is started.
As the result that such control is effected, there may be brought about problems as stated in the following (1) and (2).
(1) In case there is caused some abnormality in the direction in which the temperature in the chamber is lowered, it is impossible to achieve the object to keep the temperature at the constant level as in the conventional example as mentioned before.
(2) since the control is effected with a high set temperature in the chamber in case there is caused the abnormality in the direction in which the temperature in the chamber is raised, unfavourable influence may be exerted upon the sample.